Within the wireless telecommunications industry, the current trend in network technology is divided between global system for mobile communications (GSM) and American National Standards Institute-41 (ANSI-41) based architectures. In many respects, GSM and ANSI-41 based networks are quite similar, with the primary differences between the two technologies relating to the protocols used to communicate between the various network entities and the operating frequencies of the communication handsets. In the near future, next generation network architectures, such as Universal Mobile Telecommunications Systems (UMTS) and General Packet Radio Service (GPRS), will likely provide the network infrastructure for large-scale wireless communications around the world. As such, even though the description herein relates primarily to GSM networks, it is understood that the present invention applies to other types of mobile communications networks, including ANSI-41, Personal Communication Services (PCS), UMTS, and GPRS networks.
A simplified GSM network architecture is illustrated in FIG. 1. As shown in FIG. 1 the exemplary GSM network environment includes a home network, generally indicated by reference numeral 100, and a visited network, generally indicated by the numeral 110. As used herein, the term “home network” is used to refer to the network in which an HLR storing the mobile subscriber's location and subscription information resides. The term “visited network” refers to the network in which a mobile subscriber is roaming. Home network 100 presented in FIG. 1 includes a home location register (HLR) 104 and a gateway mobile switching center (GMSC) 106. Similarly, visited network 110 includes a GMSC 112, a first mobile switching center (MSC) 114 and associated visitor location register (VLR) 116, and a second MSC 120 and associated VLR 122. Also illustrated in FIG. 1 are a pair of base station system (BSS) units 118 and 124, which are associated with MSC 114 and MSC 120, respectively.
An HLR is a database, used to store subscriber information for a particular GSM service provider's subscribers. Functionally, an HLR is linked through a signaling network to other service areas such that subscriber information may be efficiently shared between geographically diverse networks. This sharing of information facilitates seamless intra- and inter-network roaming. A VLR, like an HLR, is also a database that contains mobile subscriber information. However, a typical VLR is closely associated (and often co-located) with a specific MSC and stores information related to mobile subscribers currently being served by that MSC.
Again, the network elements described above (HLRs and VLRs) can be thought of as essentially databases or database processing nodes. Unlike these database nodes, MSCs and GMSCs are generally identified as network switching elements that support or process both signaling and bearer (e.g., voice) type traffic. Among their many functions, MSCs and GMSCs are responsible for determining which cell site will take possession of a call. Such handoff control is facilitated by a communication link between an MSC and an associated BSS. A GMSC may also provide connectivity to one or more foreign or remote networks; otherwise, MSC and GMSC functionality is very similar.
When a mobile subscriber roams within the coverage areas of different MSC nodes, standard GSM network location updating procedures are employed to keep the mobile subscriber's HLR informed of the current location of the mobile subscriber. For example, as mobile subscriber 126 shown in FIG. 1 roams from the service area associated with MSC 114 to that of MSC 120, a number of signaling messages are generated by and communicated between MSC 114, VLR 116, MSC 120, VLR 122, GMSC 112, GMSC 106, and HLR 104. Again, the goal of such signaling activity is to provide the mobile subscriber's HLR with the information necessary to locate the roaming mobile subscriber within a home or visited network and to provide the VLR with the information necessary to complete calls to the roaming subscriber. A detailed discussion of such location or call management signaling operations can be found in The GSM System for Mobile Communications by Michel Mouly and Marie-Bernadette Pautet, Cell & Sys 1992.
FIG. 2 is an exemplary signaling message flow diagram associated with a typical location update operation triggered by roaming mobile subscriber 126 shown in FIG. 1. When mobile subscriber 126 roams into the coverage area served by MSC 120, mobile subscriber 126 registers with MSC 120 (line 1), which triggers a location update transaction. VLR 122 generates a signaling system 7 (SS7) mobile application part (MAP) UpdateLocation signaling message, which is routed to the mobile subscriber's HLR 104 (line 2). The UpdateLocation message includes information identifying the new serving MSC and VLR (MSC 120 and VLR 122). The mobile subscriber's HLR 104 receives and processes the UpdateLocation message and, in response, sends the serving VLR information related to the roaming mobile subscriber 126 (line 3). This mobile subscriber information is conveyed to VLR 122 in a MAP InsertSubscriberData signaling message. VLR 122 receives and processes the InsertSubscriberData message and responds to HLR 104 with an InsertSubscriberData_Ack message (line 4). The location updating transaction is concluded when HLR 104 sends an UpdateLocation_Ack message to VLR 122 (line 5). HLR 104 informs former serving VLR 116 that mobile subscriber 126 has roamed into a new MSC/VLR service area. Consequently, the mobile subscriber's information may be deleted from the former serving VLR database. In a GSM network, such instructions are communicated to a VLR via a MAP CancelLocation signaling message. In Line 7, VLR 116 acknowledges that the location information has been deleted with a CancelLocation_Ack message.
In the network architecture described above, no information is shared between VLR nodes within the same visited network. As a result, each time a mobile subscriber roams from one serving MSC/VLR to another within the same network, a number of signaling messages must be routed back to the mobile subscriber's home network to access the mobile subscriber's HLR data. As the number of mobile subscribers increases and the amount of inter-network roaming increases, the inefficiency and costs associated with such an architecture become significant. Furthermore, there is presently a great deal of interest in so-called “micro-cell” wireless network architectures. Micro-cell wireless network architectures include a large number of relatively small base stations and MSC nodes, as opposed to current architectures, which employ a relatively small number of large base stations and MSC nodes. In such micro-cell architectures, MSC/VLR (or MSC/VLR functional equivalent) service areas may be greatly reduced in size. As a result, the frequency of roaming between MSC/VLR service areas may be significantly increased, along with the frequency of location updating type transactions in the network.
In response to the location updating issues described above, various entities in the wireless communication industry have proposed a solution known as a gateway location register (GLR). A detailed discussion of GLR functionality can be found in 3rd Generation Partnership Project; Technical Specification Group Core Network; Gateway Location Register (GLR)—Stage 2 (Release 1999), 3G TS 23.119 v3.0.0 (2000–03), the disclosure of which is incorporated herein by reference in its entirety.
The above-referenced industry standards publication describes a GLR entity that receives and processes certain signaling messages in a mobile network. A GLR entity, as described, provides temporary local storage for subscriber information associated with non-home mobile subscribers roaming in the wireless network served by the GLR entity. That is, a GLR entity requests, receives, and temporarily caches information associated with a roaming mobile subscriber. The GLR entity distributes this information to VLR nodes in the local network as required. In essence, a GLR entity behaves in a manner similar to a VLR during transactions with an HLR and in a manner similar to an HLR during transactions with a local VLR.
While in theory such GLR functionality has the potential to significantly optimize location updating type transaction processing across network boundaries, the above-referenced industry standards publication does not address problems associated with implementing such an entity in a moble communications network. For example, adding a stand-alone GLR node to an existing wireless network would require an SS7 point code to be allocated for the GLR node. However, point codes are becoming a scarce and consequently valuable commodity. Also, many network operators do not wish to deploy new point codes unless absolutely necessary because it involves re-provisioning of other network nodes, and there are usually regulatory fees involved. Furthermore, SS7 routing rules within other nodes in the wireless network would also require modification to reflect the addition of the new GLR node to the network. From a network operations standpoint, the administration of a new GLR network element would also entail a significant amount of effort and cost. Therefore, there exists a long-felt need for a cost-effective, efficient solution to the location management problems of conventional mobile communications networks.